Teunissen Teunissen van Manen, M.L., Jansen, B., Cuesta, F., León-Yánez, S., Gosling, W.D., 2020. From leaf to soil: - alkane signal preservation, despite degradation along an environmental gradient in the tropical Andes. Biogeosciences Discussions 2020, 1-31.

https://www.biogeosciences-discuss.net/bg-2019-456/ n Plant wax -alkane biomarkers obtained from ancient soils and sediments have been used to reconstruct past n environmental changes. However, the interpretation of these ancient -alkane patterns relies primarily on our n n understanding of modern plant wax -alkane patterns measured from leaves. Very little is known about how - alkane patterns might be altered during the process of transfer from leaves into soil. Therefore our n interpretations of the ancient -alkane biomarker signal could be confounded by an unobserved bias caused by n degradation processes. Here we present the -alkane patterns extracted from leaves, necromass and soil samples n n to clarify whether the -alkane pattern, the -alkane signal, and the local environmental information reflected in n n the -alkane signal degrade, as the plant source material degrades in the tropical Andes. We find that the - n alkane patterns do degrade, but that the -alkane patterns and signal remain similar across sample types. We n n find that the -alkane patterns primarily reflect changes in longer vs. shorter -alkanes, captured by the average n chain length (ACL) and the C / (C + C ) ratio (ratio), regardless of sample type. Additionally, soil sample - 31 29 31 n alkanes secondarily reflect changes in carbon preference index (CPI) whereas leaf and necromass -alkanes do n not. We find that in all sample types the primary observed -alkane signals correlate significantly with the n n environment, temperature in particular, but that soil -alkane correlations are muted compared to leaf -alkanes. n The secondary -alkane signal (CPI) in soils also correlates significantly with the environmental signal, temperature in particular. Our results are an important step towards better understanding the taphonomy of the n n -alkane signal in the tropics, and suggest that environmental information is preserved in the -alkane signal, despite the observed degradation.

Theulé, P., Endres, C., Hermanns, M., Bossa, J.-B., Potapov, A., 2020. High-resolution gas phase spectroscopy of molecules desorbed from an ice surface: A proof-of-principle study. ACS Earth and Space Chemistry 4, 86-91.

https://doi.org/10.1021/acsearthspacechem.9b00246 High-resolution gas phase spectroscopy techniques in the microwave, millimeter-wave, and terahertz spectral ranges can be used to study complex organic molecules desorbed from interstellar ice analogue surfaces with a high sensitivity. High-resolution gas phase spectroscopy gives unambiguous information about the molecular composition, the molecular structure, and transition frequencies needed for their detection by radio telescopes in various interstellar and circumstellar environments. The results will be useful not only for interpreting astronomical spectra and understanding astrophysical processes, but also for more general studies of gas-surface chemistry. This paper presents a new experimental approach based on a combination of a chirped-pulse Fourier transform microwave spectrometer detection and a low temperature surface desorption experiment. The experimental set-up is benchmarked on the desorption of ammonia ice detected by high-resolution gas phase microwave spectroscopy.

Þorsteinsdóttir, G.V., Blischke, A., Sigurbjörnsdóttir, M.A., Òskarsson, F., Arnarson, Þ.S., Magnússon, K.P., Vilhelmsson, O., 2019. Gas seepage pockmark microbiomes suggest the presence of sedimentary coal seams in the Öxarfjörður graben of northeastern Iceland. Canadian Journal of Microbiology 66, 25-38.

https://doi.org/10.1139/cjm-2019-0081 Natural gas seepage pockmarks are found off- and onshore in the Öxarfjörður graben, Iceland. The bacterial communities of two onshore seepage sites were analysed by 16S rRNA gene amplicon sequencing; the geochemical characteristics, hydrocarbon content, and the carbon isotope composition of the sites were also determined. While one site was found to be characterised by biogenic origin of methane gas, with a carbon 13 isotope ratio (δ C (‰)) of -63.2, high contents of organic matter and complex hydrocarbons, t he other site 13 showed a mixed origin of the methane gas (δ C (‰) = -26.6) with geothermal characteristics and lower Proteobacteria organic matter content. While both sites harboured as the most abundant bacterial phyla, the Deltaproteobacteria Alphaproteobacteria were more abundant at the geothermal site and the at the biogenic